In an earlier oven design per DE 100 47 016 A1, cooling air is drawn in between an outer pane and a neighboring intermediate pane, from there into the space or cavity between two intermediate panes and finally into the space between an intermediate pane and the inner pane, ultimately to be exhausted again. The cooling of the outer pane, however, is obtained at the expense of an effective cleaning of the inner pane by pyrolysis.